Methodology has been developed for the rapid in vitro assay of chemotherapeutic drug effectiveness on human transitional cell malignancy (TCM). Drug killing of tumor cells is determined by percent inhibition in cell uptake of radioactive precursors of DNA, RNA, and protein. The assay requires only small amounts of tissue and is completed within seven days. To assess the predictive value of this in vitro assay for the in vivo effectiveness of chemotherapeutic agents, responses of human tumors growing in athymic nude mice are being determined. Mice bearing human TCM are being treated with anti-tumor drugs and their effects estimated by change in tumor size. In vitro drug profiles are being determined for tumors removed from control mice receiving no drugs. In addition, in vitro drug profiles will continue to be constructed for surgical specimens. The in vitro drug profiles will be compared to in vivo profiles from nude mouse supported tumors and to clinical data on patients undergoing chemotherapy. If the two drug profiles are similar, the in vitro assay would make possible in advance of therapy the selection of the most effective drugs for each individual patient.